This invention relates to cushioning pads, mattresses, and seats for supporting patients and others who must spend long periods in prone or seated positions. More particularly, the invention relates to a system for variably adjusting the distribution of supporting force imposed over a support area of a person's body by a gel-filled cushioning device so as to reduce the incidence of decubitus ulcers (bed sores).
A substantial number of mattresses and mattress pads have been developed in the past having as their objective the reduction of the incidence of decubitus ulcers in patients and others who must spend long periods in bed. These prior devices comprise flexible enclosures containing various cushioning materials such as air, liquid, gel, foam or granular materials as disclosed, for example, in U.S. Pat. Nos. 4,163,297, 4,454,615 and 4,628,557. Cushioning devices of the type shown in U.S. Pat. Nos. 4,163,297 and 4,628,557 further include a plurality of small pillow-like elements or inserts to permit the support surface configuration to be varied by the addition or removal of the pillow elements or inserts as the case may be, thereby enabling some adjustability of the distribution of the supportive force over the person's body. However, only adjustability in relatively large increments is provided by the addition or subtraction of such pillow elements or inserts, providing only a gross approximation of the optimum distribution of supporting force required by any particular patient depending on his individual weight, body shape, and posture required by his particular medical condition.
In an attempt to meet the need for a finer, more infinite variability in the adjustment of cushioning devices for patients, mattresses have been proposed having separate internal cells which are selectively inflatable and deflatable by connection with a set of patient-operated or automatically-operated valves which alternatively supply pressurized air to, or exhaust air from, the individual cells. While such a system provides infinitely-adjustable variability, as opposed to variability by gross increments, valving and controls therefor make the system expensive. More important, such a system of inflation and deflation is practical only if employed with an air-filled mattress where the individual compartments can thus be easily filled from, and exhausted into, the surrounding air. Unfortunately, air-filled mattresses do not produce the lowest skin-surface pressures. Rather, the lowest skin-surface pressures are obtained using a gel as the cushioning material, as taught, for example, by Berjian, et al., "Skin Pressure Measurements On Various Mattress Surfaces In Cancer Patients," 62 American Journal of Physical Medicine 217 (1983).
Accordingly, what is needed is a gel-containing cushioning device having separate compartments selectively capable of receiving or exhausting gel in infinitely variable increments to obtain infinitely variable adjustability of the distribution of supporting force on a person's body, together with an inexpensive external system for selectively receiving or delivering the gel as needed.